Chemistry ofC-Trimethylsilyl-Substituted Heterocarboranes. 19. Synthetic and Structural Studies on Trinuclear Ln(III) Carborane Clusters [Ln(III) = Sm, Gd, Tb, Dy, Ho]. I. Conversion to Sandwiched Manganese(II) and Cobalt(III) Carborane Complexes

The reaction of closo-exo -4,5-Li(THF) 2 -1-Li(THF) 2 -2,3-(SiMe 3 ) 2 C 2 B 4 H 4 with anhydrous LnCl 3 (Ln = Sm, Gd, Tb, Dy, Ho), in a molar ratio of 2:1 in dry benzene (C 6 H 6 ), produced the sandwiched paramagnetic species {[η 5 -1-Ln-2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 ] 3 [(μ 2 -1-Li-2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 ) 3 (μ 3 -OMe)][μ 2 -Li(C 4 H 8 O)] 3 (μ 3 -O)} (Ln = Sm ( 1 ), Gd ( 2 ), Tb ( 3 ), Dy ( 4 ), Ho ( 5 )) in 59%, 58%, 49%, 52%, and 59% yields, respectively. All compounds were characterized by IR spectroscopy and by single-crystal X-ray diffraction studies; compound 1 was also characterized by 1 H, 11 B, and 13 C NMR spectroscopy. Compounds 1 − 5 are isostructural clusters consisting of three half-sandwich lanthanacarboranes, three lithiacarboranes, three bridging lithium atoms, and three THF molecules of solvation. Their structures are such that the nine metal atoms form a tricapped trigonal prism with the lanthanide metals at the capping positions. The reaction of 2 with MnCl 2 in benzene, followed by the addition of TMEDA, gave a dinuclear manganacarborane sandwich complex, 4,4‘,5,5‘-Mn(TMEDA)-1,1‘- commo- Mn[2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 ] 2 ( 6 ). Compound 6 was characterized on the basis of its elemental analysis and IR spectrum and also by X-ray diffraction. The reaction of 1 with CoCl 2 in dry benzene, followed by the addition of TMEDA, gave the cobalt(III) sandwich complex, Li(TMEDA) 2 {1,1‘- commo- Co[2,3-(SiMe 3 ) 2 -2,3-C 2 B 4 H 4 ] 2 } ( 7 ). Complex 7 was characterized on the basis of 1 H, 7 Li, 11 B, and 13 C NMR spectra and IR spectra and also by X-ray diffraction.